Solvent extraction of hydrocarbon oils



Patented Oct. 17, 1939 PATENT OFFICE SOLVENT axmacrg ig or mmnocmmon Oldrlch S. Pokorn'y and George W. Gurd, Sarnia, Ontario, Canada, assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 31, 1938, Serial No. 248,875

12 Claims.

This invention relates to the selective solvent extraction of hydrocarbon oils, and is more particularly concerned with the extraction of aromatic and/or olefinic hydrocarbons from lighter hydrocarbon oils.

Light hydrocarbon oils such as naphthas generally contain a mixture of paraflinic, olefinic and aromatic hydrocarbons. The relative proportions of each depend very largely upon the crude fromwhich the naphtha is obtained and method of production. It has been found that the aromatic fractions of naphthas are characterized by high octane number which makes them especially suitable for anti-detonation motor fuels either alone or in blends with other fuels of lower octane number. The aromatic fractions are also especially useful as solvents for lacquer, paints, varnishes, enamels and coating compositions generally. The oleflnes are chemi- .cally reactive and it is often desired to separate these from paraflin fractions.

Various methods have been proposedfor separating the parafiinic from the olefinic or aromatic hydrocarbons in order to obtain a highly olefinic or aromatic fraction. The simplest of these methods is solvent extraction in' which the naphtha is treated with a solvent which has a preferential solvent power for aromatics or olefins and relatively little or no solvent power for I solvents for extracting aromatic or olefinic hydrocarbons from naphthass The nature of these solvents and the manner of using them will be fully understood from the following description: It has been found that monophenolic ethers of ethylene glycol and polyethylene glycols and their derivatives, such as the monophenyl or vmonotolyl ethers of such glycols, have high selective solvent power for olefinic and aromatic hydrocarbons, and are suitable for extracting them from mixtures with paraflinic hydrocarbons. The solvents of this type may be described generally by means of the following structural formula:

where n is at least 2, and the ring should be taken as representative of any aromatic ring: also where R can be either hydrogen atom or alkyl radical. Monophenyl and monotolyl ethers of ethylene glycol, di-ethylene glycol, tri-ethylene glycol, tetraethylene glycol and pentaethylene glycol are suitable. Specific examples are mono-phenyl ether of ethylene glycol (which is frequently named beta-phenoxy ethyl alcohol) and beta-phenoxy propyl alcohol. These solvents ma'yalso be. used in admixture with di-ethylene glycol, tri-ethylene glycol, tetraethylene glycol and also dioxy derivatives of the glycol series CnH2n+202, such as ethylene, propylene and bu- .tylene glycols, tri-, tetraand pentamethylene glycols, etc.-

Beta phenoxy ethyl alcohol is the monophenyl ,ether of ethylene glycol and has the following properties:

Specific gravity at F 1.112

Boiling point at 760 mm. Hg 458 F. Refractive index at 20 C 1.5390

Benzene, toluene and xylene are completely miscible in all proportions with beta phenoxy ethyl alcohol at F. A-Mid-Continent naphtha having a boiling range between 192 and 288 F. and a gravity, A. P. I., of 61.3 is completely miscible with an equal volume of betaphenoxy ethyl alcohol only at 170 F.

.In carrying out the extraction, the naphtha is first mixed with from to 200% of beta phenoxy ethyl alcohol. The mixture 'is heated, if necessary, to a temperature between 50 and F. and allowed to settle. The two layers formed are separated, and the aromatic hydrocarbons recovered from the bottom or extract layer by distillation or other suitable means.

The extraction may also be carried out in a continuous counter-current manner either ,in a single tall tower or in a series of stages.

Mixtures of the phenoxy alcohols with triethylene glycol or other glycols mentioned above frequently exhibit greater selectivity than the phenoxy alcohol alone. Mixtures of approximately equal proportions of each solvent, for

example, are suitable, although other mixtures can be used.

It is also frequently advantageous to add from Source Mid-Continent crude Gravity, 'API 61.3

Refractive index at C 1.4080

Aniline points. 132F.

Initial boiling point 192 F.'

% off at.. 220 F.

Final boiling point 288 F.

The gravity and refractive index of the blend are as follows:

Gravity, API 56.3 Refractive index at 20 C 1.4208

This synthetic blend is then extracted in a seven-stage counter-current treater with various amounts of beta phenoxy ethyl alcohol, either alone or in admixture with triethylene glycol and water. The counter-current treatment is carried out at about F. in the usual manner. Before obtaining final inspections on the rafllnate phase, the raflinate is water-washed to a. constant refractive index. The extract is recovered from the extract phase by steam distillation. The overhead from the steam'distillation is collected in iced receivers to prevent loss of light ends and is then waterwashed to a constant refractive index. The solvent is dehydrated by vacuum distillation and reused.

Example 1 J The synthetic blend is treated at 70 F. with 75% of beta phenoxy ethyl alcohol. The yields and characteristics of the raflina'te and extract are as follows:

Example 3 The blend is treated at 70 F. with 150% of a mixture of 50% beta phenoxy ethyl alcohol and 50% triethylene glycol. The results are as fol- The blend is treated at 70 F. with 150% of a mixture consisting of 50% beta phenoxy ethyl alcohol and 50% triethylene glycol. In this experiment water is added to the extract phase at the end of the treater in an amount of about 50% of the volume of extract present in the extract phase. The results are as follows:

Raflinate Extract Gravity, API so. a sac Refractive index at 20 C 1. 4110 1. 4090 Aniline point ..F 126 Yield on charge..- "percent; 83. 0 17. 0

It will be observed that whereas the refractive index of the original blend is 1.4208, the refractive index of the railinate obtained in each of the above examples is between 1.4081, as in Example 1, and 1.4120, as in Examples 2 and 4, indicating that the raflinate phase is approaching, very closely the original naphtha content of the blend ample 1, it should be noted that the refractive index of the rafllnate is 1.4081, indicating that this rafflnate issubstantially the same as the original naphtha.

Example 5 To illustrate the use of other selected solvents, phenoxy propanol was employed. The feed stock extracted was a synthetically prepared mixture of aromatics with naphtha (boiling range which has a refractive index of 1.4080. In 1112- 100-320 F.) which had been carefully treated with sulfiu'ic acid. The extraction temperature was 38 F. and 100 parts of the phenoxy propanol were used to 100 of the feed in a single batch extraction.

Rafilnate Extract reed x ract Rafllnate ry) y) Gravity, API 01. a 47. 7 Refractive index at 20 0 m1 1. 4 32 Refractive index l. 4152 1. 4174 1.4175 Aniline point ...F-- 133 Percent aromatics- S. 5 1i. 5 5. 5 Yield on'charge .-percent.- 64.8 30. 2 Yield onfeed ..percentr. 50 50 The yield and efliciency can be improved by Example 2 counter-current methods of extraction.

The blend is treated at 1 with of a mixture containing 92% betaphenoxy ethyl alcohol and 8% water. The results are as follows:

Raflinatc Extract Gravity, API 00.1 45.0 Refractive index at 20 C. 1.4120 1. 4507 Aniline point .F Yield on charge.-. -pereent. 76. 3 W. 7

Example 6 Using cresoxy ethanol at 37 F. in a similar synthetic blend of aromatics and paramnic naphtha, with a single batch treat with 28.6% of solvent, the results were as follows:

Sample 7 To illustrate the removal of olefins from paraiilns a synthetic mixture of amylene and hexane was made up andextracted with 85.2 parts of phenoxy propanol per 100 parts of feed at 50 'F, in a single batch extraction. The feed contained 18.6% of oleflns, and the extract which amounted to 37% by volume contained 21.2%

' oleflns. Counter-current methods willimprove these results.

trample 8 Using a 72.5% treat with cresoxy ethanol at 50 F. in a single batch extraction, a mixture containing 44.5% amylene and 55.5% hexane gave 36.2% by volume of an extract (dry) which under any conditions and in all the various modiflcations which have been proposed for solvent treating processes in connection with other selective solvents. By way of illustration, but not of limitation, such modifications include withdrawal of extract, addition of water or other modifying agent thereto and subsequent return of cycle oil to-the treating step; the use of'other solvents having preferential selective solventpower for paraiiinlc hydrocarbons in coniunc-' tion with the phenoxy alcohol; the of a temperature gradient in the treating tower or from stage to stage; the combination. of a cracking or destructive hydrogenation process with the solvent treating process; the combination of the solvent treating process with a subsequent hydrogenation or hydroflning of'the ex.- tract, etc.

The present application is a'contlnuation in par; of Serial No. 162,875 ,filed BeM 18, 193 o v This invention is not limited by details which have been given merely for-"pur tention to claim all novelty inherent in the iiivention. 1 We claim:-.

,1. The method of separating paramnic hydrocarbons from mixtures containing thesame with non-paramnic fractions, which comprises extracting the mixture with-a solvent comprising an aromatic ether of a glycol whereby the nonparafllnic fractions are concentrated in the, solvent.

2. The method of separatingparafiinic hydrocarbons from mixtures containing the same with non-paraflinic fractions, which comprises extracting the mixture with a solvent comprising a'monophenolic ether of a glycol, whereby the non-paramnic fractions are concentrated inthe solvent.

3. The method of separating parafllnic hydrocarbons from mixtures containing the same with non-paraflinic fractions, which comprises extracting the mixture with a solvent comprising a monophenyl'ether of a. glycol, whereby the non-paraiilnic fractions are concentrated in the solvent.

4. The method of separating parafllnic hydrocarbons from mixtures containing the same with non-paraiilnic fractions, which comprises extracting the mixture with a solvent comprising beta phenoxy ethyl alcohol, whereby the non-paraflinic fractions are concentrated in the solvent.

5. The method of separating paraflinic hydrocarbons from mixtures) containing the'same with non-paraiiinic fractions, which comprises,

extracting the mixture with a solvent comprising: beta phenoxy ethyl alcohol and a polyethylene glycol, whereby the non-parafllnic fractions are concentrated in the solvent.

6. The method of separating parafilnic hydrocarbons from mixtures containing the same with non-parafllnic fractions, which comprises.

extracting the mixture with a solvent comprising beta phenoxy ethyl alcohol, triethylene glycol and 5 to 8% of water, whereby the non-paramnic fractions are concentrated in the solvent.

'I. The method of obtaining a highly aromatic fraction from a naphtha containing aromatic and parafllnic hydrocarbons which comprises extracting the naphtha with a solvent comprising a monophenolic ether of a glycol, separating the two phases thereby formed and recovering the aromatic hydrocarbons from the extract phase.

. 8. Process according to claim 7 in which the solvent comprises beta phenoxy ethyl alcohol.

9. Process/according to claim 7 in which the esolvent coniprises beta phenoxy ethyl alcohol and 1 triethylel'i'e -alilcol. any theories; of the mechanism of thereactions'nor'byfanyi lliProcessfaccording to claim 7 in which the 1; s olvent' comprises beta phenoxy ethyl alcohol. triethyleneia v ol and 5 to 8% of water.

poses of illustratiombut is-limited only in and V by the following claims in which it is ojur in-v alcohol.

QLDRICHI S. POKORNY.

GEORGE W. GURD. 

